This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Heparan sulfate (HS) mutant endothelial cell (EC) lines represent an ideal system for examining the structure-function relationships of HS co-receptors in a cellular context with direct implications to physiology and pathology in vivo. We previously established an experimental procedure to generate immortalized EC lines from mice deficient in Ndst1 and Ndst2. Within this funding period, we are pursuing the generation of new mouse EC lines that are deficient in different HS biosynthetic genes or their combinations.